1. Field of the Invention
The present invention relates to a resettable combination lock, more particularly one, which can be easily reset, and which can be easily adapted to suit doors of different thicknesses.
2. Brief Description of the Prior Art
Combination locks are convenient to use because they can be unlocked without use of a key, and there won't be risk of losing the key.
Referring to FIGS. 14 to 17, a conventional resettable combination lock includes a lock member 10 secured on an outer side of a door 40, a back cover 20 securely connected to an inner side of the door 40 and the lock member 10, and a knob 30.
The lock member 10 includes:
a housing 101 formed with two rows of spaced holes 102 thereon, which are given respective numbers or symbols;
several buttons 103 held in respective ones of the holes 102 of the housing 101, which includes a restoring button, which can be pressed for making the other buttons released from the pressed position; each button 103 has a spring 160 held therein;
a main body 104 securely held in the housing 101; the main body 104 is formed with two rows of spaced holding holes 105 thereon, which face respective ones of the holes 102 of the housing 101;
several locking plates 50 passed through respective ones of the holes 105 of the main body 104, touching the corresponding springs 106 at upper ends (according to FIG. 16); there are first and second types of locking plates 50; each of all the locking plates 50 has both a small gap 502 and an engaging protrusion 503 on an inwards-facing edge, and has a big gap 501 on an outwards-facing edge; the first type have their big gaps 501 near to upper ends thereof while the second type have their big gaps 501 near to lower ends thereof; each engaging protrusion 503 has a sloping side;
a rear cover 108 securely connected to a rear end of the housing 101;
several springs 107 touching the rear cover 108 at first ends and touching respective ones of the locking plates 50 at second ends for biasing the locking plates 50 upwards (according to FIG. 16);
an engaging plate member 70 having a lengthways extending big slot 701 thereon, and several small gaps 702 spaced along two long sides of the inner edge, communicating with the slot 701; the engaging plate member 70 is positioned next to the main body 104, around the locking plates 50 and linearly displaceable relative to the main body 104 in the direction of the long sides thereof; and
an elongate detaining member 60 up and down movably arranged between the two rows of locking plates 50; the detaining member 60 has hooked elastic engaging portions 601, which are spaced apart along two long sides thereof, and which face respective ones of the locking plates 50 for releaseably detaining the locking plates 50; the detaining member 60 is connected to the restoring button such that it will move to a lower position (according to FIG. 16) and disengage the locking plates 50 as soon as the restoring button is pressed.
The knob 30 and a dead bolt 301 are connected to the housing 101 in such a way that the dead bolt 301 will retreat into and project out from the housing 101 as soon as the knob 30 is turned. And, the knob 30 is connected to the engaging plate member 70 in such a way that it can be turned only when the engaging plate member 70 is free to move without being stopped by the locking plates 50.
When the numbered buttons are pressed, the locking plates 50 will move towards the rear cover 108, with the sloping sides of the engaging protrusions 503 sliding on the hooked elastic engaging portions 601 of the detaining member 60. Consequently, the engaging portions 601 of the detaining member 60 will engage the locking plates 50 to detain the same in the pressed position.
The locking plates 50 will project into the small gaps 702 of the engaging plate member 70 to prevent the plate member 70 from moving when the combination lock locks. And, when the numbered buttons are pressed according to the unlocking combination, i.e. all of the locking plates 50 of the first type are in the pressed position, and also none of the locking plates of the second type are in the pressed position, all of the big gaps 501 will face the engaging plate member 70. Consequently, the engaging plate member 70 will be free to move without being stopped by the locking plates 50, and in turns the knob 30 can be turned so as to retreat the dead bolt 301 into the lock member 10.
Because the buttons will be polished after they have been pressed many times, the user should reset the combination lock occasionally in order to prevent thieves from telling the frequently pressed buttons from the rarely pressed ones of the lock from the appearance, thus finding out the unlocking combination. To reset the combination lock, one has to carry out the following steps:
(1) removing the lock member 10 from the door, and separating the rear cover 108 from the housing 101;
(2) removing the springs 107;
(3) removing the locking plates 50 by means of pliers while making the restoring button stay in the pressed position such that the locking plates 50 are free to move without being stopped by the detaining member 60;
(4) relocating locking plates 50 of the first and the second types in the holes 105 of the main body 104 according to the new unlocking combination; and
(5) fitting the springs 107 and the rear cover 108 back to the housing 101, and securing the whole lock member 10 to the door.
From the above description, it can be understood that the above conventional lock has the following disadvantages:
1. Because locking plates 50 of the first type are different from the second type in respect of position of the big gaps 501, the user has to relocate the locking plates in the holding holes 105 of the main body 104 with the help of tools in order to change the combination. Therefore, it takes much time and labor to reset the lock.
2. It is relative difficult to remove the locking plates from the holding holes 105, even with pliers, because the holes 105 are narrow. Consequently, the user will get some trouble with resetting the lock.
3. To reset the lock, the user has to first remove the lock member 10 from the door, and separate the rear cover 108 from the housing 101, and remove the springs 107 as well as relocating the locking plates, and finally he has to connect the rear cover back to the housing, and the lock member back to the door. Therefore, it takes a lot of time and labor to reset the lock. Furthermore, the springs are prone to get lost during the course of the above resetting action.
4. In removing the locking plates, the user has to keep the detaining member 60 in the pressed position by means of pressing the restoring button such that the locking plates 50 are free to move without being stopped by the detaining member 60. Consequently, the user has to press the restoring button with one hand, and hold pliers with the other.
5. There are two types of locking plates whose big gaps are formed in different positions. Therefore, the cost of manufacturing and material management will increase, and one can locate the two types of locking plates in wrong holding holes 105 while assembling the lock.